Self-cleaning long-wave infrared optical filter and preparation method thereof

Abstract

The invention discloses a self-cleaning long-wave infrared optical filter and a preparation method thereof. The optical filter comprises an optical filtering structure, a protective layer and a self-cleaning layer. The light filtering structure comprises an infrared transparent substrate and a light filtering layer located on one side of the infrared transparent substrate. The protective layer covers the surface of the side, away from the infrared transparent substrate, of the light filtering layer, covers the partial surface, facing the light filtering layer, of the infrared transparent substrate, and covers the side wall of the light filtering layer. The self-cleaning layer is located on the side, away from the infrared transparent substrate, of the protective layer and comprises at least one or more of a hydrophobic layer, a catalytic decomposition layer and a conductive heating layer. Through the arrangement of the technical characteristics, the anti-pollution capability of the optical filter can be improved, so that the optical filter keeps stable spectrum transmittance under the conditions of long-term operation and complex environment exposure.

Description

Technical Field

[0001] This application relates to the field of infrared optical device technology, and more specifically, to a self-cleaning long-wave infrared filter and its preparation method. Background Technology

[0002] Long-wave infrared (LWIR) spectral range typically refers to the 8-14 μm band. This band lies within the atmospheric window region and possesses excellent transmission performance, thus it is widely used in thermal imaging systems, gas detection equipment, and environmental monitoring devices. Currently, commonly used LWIR filters typically employ a multilayer dielectric interference film structure. By rationally designing the film structure, bandpass filters, long-pass filters, or short-pass filters can be realized.

[0003] However, in real-world applications, infrared filter surfaces are susceptible to various contaminants, such as moisture adsorption from the air, oil mist deposition in industrial environments, volatile organic compound (VOC) pollution, and dust particle deposition. These contaminants often exhibit strong absorption characteristics in the long-wave infrared band, significantly reducing the filter's infrared transmittance and leading to a decline in system imaging quality. Furthermore, contaminant adhesion can cause scattering loss and spectral drift. Summary of the Invention

[0004] In view of the above-mentioned deficiencies of the related technologies, the technical problem to be solved by this application includes at least how to improve the anti-pollution ability of the filter so that the filter has a stable spectral transmittance under complex environmental conditions.

[0005] To address at least one of the aforementioned technical problems, this application proposes a self-cleaning long-wave infrared filter and its preparation method.

[0006] According to one aspect of this application, a self-cleaning long-wave infrared filter is provided, comprising: The filter structure includes an infrared transparent substrate and a filter layer located on one side of the infrared transparent substrate; The protective layer covers the side surface of the filter layer away from the infrared transparent substrate, the part of the infrared transparent substrate facing the filter layer, and the sidewalls of the filter layer. The self-cleaning layer is located on the side of the protective layer away from the infrared transparent substrate. The self-cleaning layer includes at least one or more of the following: a hydrophobic layer, a catalytic decomposition layer, and a conductive heating layer.

[0007] In some embodiments, the self-cleaning layer includes: A conductive heating layer covers the surface of the protective layer away from the infrared transparent substrate; At least one electrode structure is located on the side of the conductive heating layer away from the protective layer and is arranged circumferentially around the filter layer.

[0008] In some embodiments, the self-cleaning layer further includes: The hydrophobic layer is located on the side of the conductive heating layer away from the infrared transparent substrate; the hydrophobic layer can be a periodic micro / nano structure or a non-periodic micro / nano structure.

[0009] In some embodiments, an external contaminant forms a contact angle with the hydrophobic layer; The contact angle ranges from 150° to 180°.

[0010] In some embodiments, the hydrophobic layer comprises a plurality of periodically arranged nanopillars.

[0011] In some embodiments, the self-cleaning layer includes:

[0012] The catalytic decomposition layer is located on the side of the protective layer away from the filter layer.

[0013] In some embodiments, the filter layer comprises multiple interference filter films, with adjacent interference filter films having different refractive indices.

[0014] According to a second aspect of this application, a method for preparing a self-cleaning long-wave infrared filter is provided, the method comprising: A filter structure is formed, which includes an infrared transparent substrate and a filter layer located on one side of the infrared transparent substrate; A protective layer is formed, which covers the side surface of the filter layer away from the infrared transparent substrate, the part of the infrared transparent substrate facing the filter layer, and the sidewalls of the filter layer. A self-cleaning layer is formed on the side of the protective layer away from the infrared transparent substrate. The self-cleaning layer includes at least one or more of a hydrophobic layer, a catalytic decomposition layer, and a conductive heating layer.

[0015] In some embodiments, the self-cleaning layer includes a hydrophobic layer and a conductive heating layer; The formation of a self-cleaning layer includes: A conductive heating layer is formed, which covers the side of the protective layer away from the infrared transparent substrate; At least one electrode structure is formed, the electrode structure is located on the side surface of the conductive heating layer away from the protective layer, and is arranged circumferentially around the filter layer; A hydrophobic layer is formed, located on the side of the conductive heating layer away from the infrared transparent substrate; the hydrophobic layer can be a periodic micro / nano structure or a non-periodic micro / nano structure.

[0016] In some embodiments, the self-cleaning layer includes a catalytic decomposition layer; The formation of a self-cleaning layer includes:

[0017] A catalytic decomposition layer is formed on the side of the protective layer away from the filter layer.

[0018] Implementing this application will have the following beneficial effects: This application discloses a self-cleaning long-wave infrared filter. In addition to introducing a protective layer to protect the filter structure, a self-cleaning layer is also provided to further improve the filter's anti-fouling ability. Specifically, the self-cleaning layer can be provided with at least one or more of the following: a catalytic decomposition layer, a conductive heating layer, and a hydrophobic layer, depending on different needs. This allows the filter to maintain high transmittance and stable spectral characteristics even in complex environments such as humidity, high dust levels, and oil mist. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure corresponding to the filter structure disclosed in the embodiments of this application; Figure 2 This is a schematic diagram of the filter structure and protective layer disclosed in the embodiments of this application; Figure 3 This is a schematic diagram of the structure of a self-cleaning long-wave infrared filter disclosed in an embodiment of this application; Figure 4 This is a schematic diagram of another self-cleaning long-wave infrared filter disclosed in an embodiment of this application; Figure 5 This is a schematic diagram of the teardrop angle disclosed in an embodiment of this application; Figure 6 This is a schematic flowchart of a method for preparing a self-cleaning long-wave infrared filter disclosed in an embodiment of this application.

[0021] Explanation of reference numerals in the attached figures: 100 - Filter structure, 110 - Infrared transparent substrate, 120 - Filter layer, 121 - First interference filter film, 122 - Second interference filter film; 200 - Protective layer; 300 - Self-cleaning layer, 310 - Conductive heating layer, 311 - Electrode structure, 320 - Hydrophobic layer, 321 - Nanopillars. Detailed Implementation

[0022] The technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] It should be noted that the terms "first," "second," etc., in this application specification, claims, and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or server that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or devices.

[0024] Various exemplary embodiments, features, and aspects of this application will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0025] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0026] In this document, the term "and / or" describes a relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists alone, A and B exist simultaneously, and B exists alone. Additionally, the term "at least one" in this document means any combination of at least two of any one or more elements. For example, including at least one of A, B, and C can mean including any one or more elements selected from the set consisting of A, B, and C.

[0027] Furthermore, to better illustrate this application, numerous specific details are provided in the following detailed description. Those skilled in the art should understand that this application can be implemented without certain specific details. In some instances, methods, means, components, and circuits well-known to those skilled in the art have not been described in detail in order to highlight the main points of this application.

[0028] This application proposes a self-cleaning long-wave infrared filter and its preparation method to address the problem that infrared filters in related technologies have limited resistance to contaminants and experience performance degradation after long-term use. The method proposed in this application will be described below with reference to specific technical features and accompanying drawings.

[0029] A self-cleaning long-wave infrared filter includes a filter structure 100, a protective layer 200, and a self-cleaning layer 300.

[0030] The filter structure 100 includes an infrared transparent substrate 110 and a filter layer 120 located on one side of the infrared transparent substrate 110.

[0031] As one implementation method, such as Figure 1 As shown, the filter structure 100 includes an infrared transparent substrate 110 and a filter layer 120 located on one side of the infrared transparent substrate 110. The center step size of the filter structure 100 can be in the range of 8 μm to 14 μm.

[0032] The infrared transparent substrate 110 provides stable support for the optical structure and a stable adhesion interface for the filter layer 120. The material selection for the infrared transparent substrate 110 includes, but is not limited to, materials with high transmittance in the long-wave infrared region such as Ge, ZnSe, Si, or ZnS. In this embodiment, ZnSe can be selected to form the infrared transparent substrate 110. The thickness of the infrared transparent substrate 110 can be set in the range of 0.3 mm to 10 mm, and can be adjusted according to the structural strength requirements of the application scenario.

[0033] The filter layer 120 includes multiple interference filter films, with adjacent interference filter films having different refractive indices. Specifically, the filter layer 120 may include multiple first interference filter films 121 and multiple second interference filter films 122. The first interference filter films 121 may be made of high-refractive-index materials, and the second interference filter films 122 may be made of low-refractive-index materials. Please refer to [link to relevant documentation]. Figure 1 The system employs an alternating structure of high-refractive-index and low-refractive-index materials, specifically an alternating structure of the first interference filter film 121 and the second interference filter film 122. Precise control of the film thickness enables transmission or cutoff of the target's center wavelength. High-refractive-index materials include, but are not limited to, Ge, ZnS, and TiO2, while low-refractive-index materials include, but are not limited to, YF3, SiO2, and Al2O3. The refractive index and thickness of the multilayer interference filter films must adhere to interference filtering conditions to achieve different filtering performances, such as long-wave infrared bandpass, long-wave pass, or short-wave pass. In the filter layer 120, 4 to 60 interference filter layers can be formed, and the thickness of the interference filter films is typically set between 0.1 μm and 10 μm.

[0034] The protective layer 200 covers the side surface of the filter layer 120 away from the infrared transparent substrate 110, covers a portion of the surface of the infrared transparent substrate 110 facing the filter layer 120, and covers the sidewalls of the filter layer 120.

[0035] As one implementation, to improve the mechanical strength and environmental stability of the filter surface and to provide an adhesion interface for the subsequent self-cleaning layer 300, a protective layer 200 can be provided on the side of the filter layer 120 away from the infrared transparent substrate 110. See also... Figure 2 In addition to covering the filter layer 120, the protective layer 200 also covers part of the surface of the infrared transparent substrate 110 to ensure that the filter layer 120 is fully isolated from the external environment, thereby providing better protection performance.

[0036] As one implementation, the material of the protective layer 200 includes, but is not limited to, Al2O3, MgF2, SiO2, or a composite layer of multiple media.

[0037] The protective layer 200 has good wear resistance, chemical corrosion resistance and thermal stability. Its thickness can generally be set in the range of 50nm to 1000nm to ensure that it does not significantly affect the spectral transmittance of the filter structure 100 while providing protection.

[0038] The self-cleaning layer 300 is located on the side of the protective layer 200 away from the infrared transparent substrate 110. The self-cleaning layer 300 includes at least one or more of the following: a hydrophobic layer 320, a catalytic decomposition layer, and a conductive heating layer 310.

[0039] In one implementation, the self-cleaning layer 300 can be arranged in an array or in a completely covered manner on the side of the protective layer 200 away from the infrared transparent substrate 110.

[0040] As a specific implementation, the self-cleaning layer 300 can be composed of at least one surface anti-fouling mechanism, namely, at least one or more of the hydrophobic layer 320, the catalytic decomposition layer, and the conductive heating layer 310. Single-layer or multi-layer structures can be combined to form a synergistic system, thereby improving the adaptability of the self-cleaning long-wave infrared filter to different polluted environments. In complex environments such as high humidity, high dust, and high oil mist, this filter can suppress transmission attenuation caused by external pollution such as water vapor adsorption, oil deposition, and dust pollution, allowing the filter to maintain stable spectral transmittance even after long-term operation and / or exposure to complex environmental conditions. Furthermore, since the self-cleaning layer 300 can improve the infrared transmittance stability of the filter structure 100 and reduce spectral performance degradation caused by pollution, the self-cleaning long-wave infrared filter disclosed in this application embodiment also has a good service life to a certain extent.

[0041] like Figure 3As shown, in this embodiment, the self-cleaning layer 300 is composed of a conductive heating layer 310, which covers the side of the protective layer 200 away from the infrared transparent substrate 110. The conductive heating layer 310 can be a transparent conductive heating structure used to remove surface moisture, frost, or volatile contaminants. The materials forming the conductive heating layer 310 include, but are not limited to, single or multiple layers of graphene films, transparent conductive oxides such as ITO or IZO, and gridded metal ultrathin films. The thickness of the conductive heating layer 310 can range from 5 nm to 200 nm, and the surface resistance can be designed from 10 Ω / sq to 1000 Ω / sq.

[0042] Correspondingly, in order to actively trigger the uniform heating of the conductive heating layer 310, when the self-cleaning layer 300 includes the conductive heating layer 310, it also includes at least one electrode structure 311.

[0043] Please continue reading. Figure 3 At least one electrode structure 311 is located on the side surface of the conductive heating layer 310 away from the protective layer 200 and is arranged circumferentially around the filter layer 120.

[0044] Specifically, the electrode structure 311 can be considered to be located on the side of the infrared transparent substrate 110 facing the filter layer 120, and arranged circumferentially around the filter layer 120. A protective layer 200 and a conductive heating layer 310 are stacked between the electrode structure 311 and the infrared transparent substrate 110. This structural arrangement can improve the reliability of the connection between the heating power supply and the filter. The specific width of the electrode structure 311 and its specific position around the filter layer 120 can be adaptively adjusted according to assembly requirements.

[0045] When a low-voltage power supply of 1V to 12V is applied, the surface of the conductive heating layer 310 can be uniformly heated in conjunction with at least one electrode structure 311, with the temperature range being between 30°C and 80°C, thereby achieving surface dehumidification, defogging, and cleaning functions. This cleaning mechanism is applicable to humid, hot, high-moisture, and condensation-prone environments.

[0046] Electrode structure 311 is a metal electrode. In a preferred embodiment, electrode structure 311 can be a double-layer metal electrode. Electrode structure 311 can be formed using Ti with a thickness of 5 nm and Au with a thickness of 50 nm. The presence of Ti enhances the adhesion between electrode structure 311 and conductive heating layer 310, while the presence of Au provides a stable conductive path, thereby ensuring the normal operation of conductive heating layer 310.

[0047] Another self-cleaning long-wave infrared filter disclosed in this application embodiment is as follows: Figure 1 , Figure 2 as well as Figure 4 As shown. With Figures 1 to 3The difference in the corresponding embodiment is that the self-cleaning layer 300 includes a hydrophobic layer 320 in addition to the conductive heating layer 310. Except for the conductive heating layer 310, the other structures, layering relationships, material settings, and parameters are the same as... Figure 3 The corresponding implementation methods are the same, and will not be described again here.

[0048] In a specific embodiment, such as Figure 4 As shown, the hydrophobic layer 320 is located on the side of the conductive heating layer 310 away from the infrared transparent substrate 110.

[0049] As one implementation method, the hydrophobic layer 320 can be a periodic micro / nano structure or a non-periodic micro / nano structure. This application embodiment uses a periodic micro / nano structure as an example for illustration. Micro / nano structures can be understood as rough structures at the micro / nano scale; please refer to [link to relevant documentation]. Figure 4 In this embodiment, the hydrophobic layer 320 includes a plurality of periodically arranged nanopillars 321. The plurality of periodically arranged nanopillars 321 form a nanopillar array.

[0050] Specifically, periodic micro / nanostructures can be arrays of nanopillars, nanocones, micro / nano composite protrusions, or pore arrays. For periodic micro / nanostructures, the arrangement period can be 0.3 μm to 3 μm; the height can be 0.1 μm to 2 μm; and the size in the periodic arrangement direction of the micro / nanostructure can be 50 nm to 500 nm.

[0051] The micro-nano structure can introduce an air interface and surface tension regulation to create a contact angle between external pollutants and the self-cleaning layer 300, so that water droplets can roll off in a humid environment, thereby significantly reducing the adhesion probability of liquid water, oil, and metal oxide dust, and reducing the formation of a contamination layer on the filter surface.

[0052] like Figure 5 As shown, an external pollutant forms a contact angle with the hydrophobic layer 320, and the contact angle θ ranges from 150° to 180°.

[0053] The self-cleaning layer 300, or hydrophobic layer 320, exhibits an apparent contact angle of 150° or greater for liquid contaminants such as water droplets, oil mist condensates, and organic solvent microdroplets. Simultaneously, the hydrophobic layer 320 possesses low adhesion characteristics with a contact angle hysteresis of less than 10°. Furthermore, the self-cleaning layer 300, or hydrophobic layer 320, exhibits low adhesion to solid particles such as dust, smoke, and oxide particles, enabling spontaneous desorption of these particles at an angle of inclination of 20° or less.

[0054] The hydrophobic layer 320 enables the self-cleaning long-wave infrared filter to automatically remove liquid contaminants such as water droplets, as well as solid contaminant particles. Building upon this, the synergistic effect of micro / nano structure design and functional materials significantly reduces the filter surface's adsorption capacity for contaminants, while simultaneously providing active or passive cleaning capabilities. This ensures long-term reliable operation of the long-wave infrared system under harsh conditions.

[0055] In another self-cleaning long-wave infrared filter disclosed in this application embodiment, the self-cleaning layer 300 may further include a catalytic decomposition layer in addition to the filter structure 100 and the protective layer 200. The catalytic decomposition layer is located on the side of the protective layer 200 away from the filter layer 120.

[0056] In one implementation, when the self-cleaning layer 300 is a single-layer structure, it can be positioned on the side of the protective layer 200 away from the filter layer 120. When the self-cleaning layer 300 is a multi-layer structure, on the side of the protective layer 200 away from the filter layer 120, a catalytic decomposition layer, a conductive heating layer 310, and a hydrophobic layer 320 are sequentially arranged in the stacking direction of the filter layer 120. Compared to a single-layer structure, a multi-layer structure can further enhance the anti-fouling ability while maintaining light transmittance without significant impact, achieving composite self-cleaning.

[0057] In one implementation, the catalytic decomposition layer can be a photocatalytic thin film structure, whose constituent materials include, but are not limited to, TiO2, ZnO, WO3, or their composites, and can be selected adaptably according to specific working scenarios and requirements. The catalytic decomposition layer is formed by sputtering deposition, ALD (atomic layer deposition), or spin coating curing, and its thickness can be set in the range of 10nm to 200nm, ensuring that it maintains the infrared transparency of the filter structure 100% while generating free radicals to decompose surface organic pollutants under light or infrared radiation. The catalytic decomposition layer enables the removal of volatile organic compounds, making the self-cleaning long-wave infrared filter suitable for industrial environments with oil fumes and volatile organic compounds, and allowing it to maintain a clean surface for a long time.

[0058] The self-cleaning long-wave infrared filter disclosed in this application achieves stable optical performance in both natural and industrial environments through a layered, synergistic composite structure. During long-term operation, the filter automatically inhibits contaminant adsorption and removes contaminants through water droplet rolling, spontaneous decomposition, or surface heating. The self-cleaning layer 300 and the protective layer 200 together constitute the surface functional area, which does not significantly increase the absorption or scattering of light entering the long-wave infrared detector, while ensuring stable center wavelength and transmittance of the filter, thus guaranteeing long-term stable spectral transmittance and imaging quality.

[0059] Furthermore, all structures and processes of the self-cleaning long-wave infrared filter disclosed in this application can be realized using existing semiconductor processing technology, large-area thin film preparation processes, and nanoimprint lithography, ensuring mass production feasibility and engineering reliability. This filter can be applied to self-cleaning infrared optical components that support large field of view, wide-angle incidence, and are adaptable to industrial environments, such as infrared imaging systems, gas detection devices, uncooled infrared focal plane detectors, and industrial infrared measurement equipment.

[0060] Correspondingly, this application also discloses a method for preparing a self-cleaning long-wave infrared filter, applicable to the self-cleaning long-wave infrared filter in any of the above embodiments. The multilayer structures are firmly bonded together through process integration, thereby forming an infrared optical surface system with long-term stability.

[0061] Figure 6 The disclosed preparation method is only an exemplary embodiment, corresponding to the method described in this application. Figure 4 and Figure 5 The disclosed embodiments. Please refer to [link / reference]. Figure 6 The method specifically includes:

[0062] Step S1: Form a filter structure, which includes an infrared transparent substrate and a filter layer located on one side of the infrared transparent substrate.

[0063] In one implementation method, an infrared transparent substrate is first prepared, and then a filter layer is deposited on one side of the infrared transparent substrate. In this embodiment, ZnSe can be selected as the material for forming the infrared transparent substrate. ZnSe exhibits excellent transmission performance in the 8μm to 14μm wavelength range, with a transmittance of 70% to 75%, and possesses good machinability and thermal stability, making it suitable for long-term exposure to complex industrial environments. This embodiment uses a 2mm thick ZnSe optical window, and its surface roughness is controlled to Ra≤1nm through a double-sided polishing process.

[0064] Furthermore, after forming the infrared transparent substrate and before forming the filter layer, in order to ensure the adhesion strength and interface cleanliness of the subsequent film layers, the infrared transparent substrate needs to undergo precision polishing and cleaning to obtain an optical-grade surface. Specific steps may include: ultrasonic cleaning with acetone for 10 minutes, ultrasonic cleaning with anhydrous ethanol for 10 minutes, rinsing with deionized water and drying with nitrogen, followed by drying in an oven at 120°C for 30 minutes to thoroughly remove moisture and volatile residues.

[0065] As one implementation method, the cleaned infrared transparent substrate should be placed in a dust-free environment for later use.

[0066] For the filter layer, multilayer interference filters can be deposited using ion beam sputtering, electron beam evaporation, or magnetron sputtering. To obtain the desired transmission window in the 8μm to 14μm range, one implementation method involves using Ge as a high-refractive-index material to form the first interference filter and ZnSe as a low-refractive-index material to form the second interference filter. The multilayer interference filter is fabricated using electron beam evaporation combined with ion-assisted deposition (IAD). The interference filter layer can have a 24-layer structure to achieve a long-wave infrared bandpass effect with a center wavelength of approximately 10.6μm and a bandwidth of approximately 3.0μm. Furthermore, the thickness error of each layer of the first and second interference filters needs to be controlled within ±1% to ensure stable bandpass characteristics.

[0067] As one implementation method, after the multilayer interference filter film is deposited, the overall structure needs to undergo annealing at 150°C for 3 to 4 hours to reduce internal stress, improve film adhesion, and enhance resistance to environmental changes. Nitrogen protection should be maintained during annealing to prevent moisture absorption or oxidation.

[0068] Step S2: Form a protective layer that covers the side surface of the filter layer away from the infrared transparent substrate, covers a portion of the infrared transparent substrate facing the filter layer, and covers the sidewalls of the filter layer.

[0069] As one implementation method, to protect the filter structure from external contact, abrasion, or etching processes, an optical protective film can be deposited on the surface of the filter layer away from the infrared transparent substrate to form a protective layer. In this embodiment, a 150 nm thick SiO2 layer can be prepared as the protective layer using atomic layer deposition (ALD). The protective layer provides a uniform and dense nanoscale interface, facilitating the subsequent construction of micro / nano structures. Simultaneously, the protective layer enhances the mechanical strength and chemical corrosion resistance of the filter, and maintains high transmittance in the 8 μm to 14 μm wavelength range without compromising the spectral characteristics of the filter.

[0070] As one implementation method, after the protective layer is deposited, a low-temperature curing process is still required to make the interface bonding between the layers more stable.

[0071] Step S3: Form a self-cleaning layer. The self-cleaning layer is located on the side of the protective layer away from the infrared transparent substrate. The self-cleaning layer includes at least one or more of the following: a hydrophobic layer, a catalytic decomposition layer, and a conductive heating layer.

[0072] As one implementation method, the formation of the self-cleaning layer depends on the selection of specific functional layers, such as which one or more of the hydrophobic layer, catalytic decomposition layer, and conductive heating layer to determine the corresponding formation process. For example, the hydrophobic layer can be formed using etching or nanoimprinting processes, or the decomposition photometric and conductive heating layers can be formed through thin film deposition.

[0073] As a preferred embodiment, after the self-cleaning layer is formed, the self-cleaning long-wave infrared filter can be subjected to structural curing, annealing and surface energy modulation treatment to form a stable filter structure.

[0074] The self-cleaning long-wave infrared filter prepared using the above method exhibits excellent anti-fouling capabilities and can be used stably for a long time without frequent manual cleaning and maintenance, thereby reducing the maintenance cost of the filter. Simultaneously, the optical matching between the self-cleaning layer and the filter layer is optimized to maintain a transmission wavelength drift of less than 5% and a transmittance attenuation of less than 3% within an incident angle range of 0° to 60°, thus ensuring long-term stable operation of the system under wide field of view and wide incident angle conditions.

[0075] In a preferred embodiment, when the self-cleaning layer includes a hydrophobic layer and a conductive heating layer, forming the self-cleaning layer includes:

[0076] A conductive heating layer is formed, which covers the side of the protective layer away from the infrared transparent substrate.

[0077] At least one electrode structure is formed, which is located on the side surface of the conductive heating layer away from the protective layer and is arranged circumferentially around the filter layer.

[0078] A hydrophobic layer is formed, located on the side of the conductive heating layer away from the infrared transparent substrate; the hydrophobic layer can be a periodic micro / nano structure or a non-periodic micro / nano structure.

[0079] Specifically, a conductive heating layer and at least one electrode structure are first formed, followed by the formation of a hydrophobic layer.

[0080] One implementation method involves preparing a single-layer graphene film using CVD and then uniformly coating the protective layer surface with graphene using a wet transfer technique to form a conductive heating layer. The thickness of the graphene is on the nanoscale, approximately 0.34 nm, to ensure stable conductivity of the conductive heating layer without significantly affecting infrared transmission.

[0081] Furthermore, to ensure a reliable connection to the heating power supply, a metal electrode structure needs to be deposited around the photofilter. A double-layer metal electrode can be formed using materials such as Ti / Au. By applying a low voltage power supply, such as 3V to 8V, uniform Joule heating can be achieved in the conductive heating layer. The surface temperature can be controlled within a range of 30℃ to 60℃, suppressing water vapor condensation and accelerating the volatilization or decomposition of some pollutants, thus facilitating efficient drainage of the subsequent hydrophobic layer's micro / nano structure.

[0082] As one implementation method, the hydrophobic layer can be formed by etching, nanoimprinting, or self-assembly processes. In this embodiment, nanoimprinting technology can be used to transfer a mold pattern with a periodically arranged array of nanopillars onto the surface. Before imprinting, the surface of the conductive heating layer needs to be properly pretreated to ensure sufficient surface adhesion to withstand the imprinting stress.

[0083] In this embodiment, the arrangement period of the nanopillars in the nanopillar array can be 850 nm; the height of the nanopillars can be 420 nm; the diameter of the end of the nanopillar closest to the conductive heating layer can be 230 nm, and the diameter of the end of the nanopillar furthest from the conductive heating layer can be 160 nm.

[0084] As one implementation method, after the micro / nano structure is cured, surface energy modulation treatment is performed. That is, the surface free energy is reduced by using a fluorinated modifier, so that the contact angle is between 150° and 180°, preferably between 150° and 160°, to ensure that liquid contaminants such as water droplets remain spherical on the surface of the hydrophobic layer and easily roll off.

[0085] The filter prepared by the above method includes a protective layer and a self-cleaning layer formed by a conductive heating layer and a hydrophobic layer. The hydrophobic layer provides extremely low water droplet adhesion, enabling rapid water droplet repulsion and contaminant roll-off in spray, water vapor condensation, or rain environments, preventing the formation of a scattering layer. The uniform heating of the conductive heating layer effectively suppresses condensation, preventing fog formation; simultaneously, during the drying and heating process, it accelerates the volatilization of some organic pollutants, keeping the hydrophobic layer's interface clean. The protective layer ensures the forming quality of the self-cleaning layer and provides a stable adhesion interface for the conductive heating layer. The synergistic effect of these three elements achieves a self-cleaning effect far superior to traditional protective layers.

[0086] Meanwhile, in terms of filter structure, this three-layer structure combines physical repulsion, thermally assisted evaporation, and interface stabilization, enabling the filter to maintain stable optical performance during long-term operation under high humidity, high dust, and high oil mist conditions.

[0087] In another embodiment, when the self-cleaning layer includes only a conductive heating layer, its formation is exactly the same as that of the self-cleaning layer including both a hydrophobic layer and a conductive heating layer, and will not be described again here.

[0088] In another embodiment, when the self-cleaning layer comprises only a hydrophobic layer, the hydrophobic layer is disposed directly on the side of the protective layer away from the infrared transparent substrate, rather than on the side of the conductive heating layer away from the protective layer. Except for the change in the position of the hydrophobic layer, its formation method is exactly the same as that of the self-cleaning layer comprising both a hydrophobic layer and a conductive heating layer, and will not be described again here.

[0089] In another embodiment, when the self-cleaning layer comprises solely a catalytic decomposition layer, forming the self-cleaning layer may include:

[0090] A catalytic decomposition layer is formed on the side of the protective layer away from the filter layer.

[0091] In another embodiment, when the self-cleaning layer includes at least one of a conductive heating layer and a hydrophobic layer in addition to the catalytic decomposition layer, the catalytic decomposition layer needs to be formed first, then the conductive heating layer needs to be formed, and finally the hydrophobic layer needs to be formed.

[0092] It should be noted that the above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application's patent. The above description is exemplary and not exhaustive, nor is it limited to the disclosed embodiments. The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims. The terminology used herein is chosen to best explain the principles, practical applications, or technical improvements in the market of the various embodiments, or to enable other those skilled in the art to understand the various embodiments disclosed herein.

Claims

1. A self-cleaning long-wave infrared optical filter, characterized in that, The method comprises: forming a filter structure, the filter structure comprising an infrared transparent substrate and a filter layer located on a side of the infrared transparent substrate; forming a protective layer, the protective layer covering a side surface of the filter layer away from the infrared transparent substrate, covering a part of a surface of the infrared transparent substrate facing the filter layer, and covering a side wall of the filter layer; forming a self-cleaning layer, the self-cleaning layer being located on a side of the protective layer away from the infrared transparent substrate, the self-cleaning layer comprising at least one or more of a hydrophobic layer, a catalytic decomposition layer, and a conductive heating layer.

2. The self-cleaning long-wave infrared optical filter of claim 1, wherein, The self-cleaning layer comprises: a conductive heating layer, covering a side surface of the protective layer away from the infrared transparent substrate; at least one electrode structure, located on a side surface of the conductive heating layer away from the protective layer, and arranged circumferentially around the filter layer.

3. The self-cleaning long-wave infrared optical filter of claim 2, wherein, The self-cleaning layer further comprises: a hydrophobic layer, located on a side surface of the conductive heating layer away from the infrared transparent substrate; the hydrophobic layer is a periodic micro-nano structure or a non-periodic micro-nano structure.

4. The self-cleaning long-wave infrared optical filter of claim 3, wherein, A contact angle is formed between an external contaminant and the hydrophobic layer, The contact angle ranges from 150° to 180°.

5. The self-cleaning long-wave infrared optical filter of claim 3, wherein, The hydrophobic layer comprises a plurality of periodically arranged nano-pillars.

6. The self-cleaning long-wave infrared optical filter of claim 1, wherein, The self-cleaning layer comprises: a catalytic decomposition layer, located on a side of the protective layer away from the filter layer.

7. The self-cleaning long-wave infrared optical filter of claim 1, wherein, The filter layer comprises a plurality of interference filter films, and the refractive indices of adjacent interference filter films are different.

8. A method for preparing a self-cleaning long-wave infrared filter, applied to the self-cleaning long-wave infrared filter according to any one of claims 1 to 7, characterized in that, The method comprises: forming a filter structure, the filter structure comprising an infrared transparent substrate and a filter layer located on a side of the infrared transparent substrate; forming a protective layer, the protective layer covering a side surface of the filter layer away from the infrared transparent substrate, covering a part of a surface of the infrared transparent substrate facing the filter layer, and covering a side wall of the filter layer; forming a self-cleaning layer, the self-cleaning layer being located on a side of the protective layer away from the infrared transparent substrate, the self-cleaning layer comprising at least one or more of a hydrophobic layer, a catalytic decomposition layer, and a conductive heating layer.

9. The method for preparing a self-cleaning long-wave infrared filter according to claim 8, characterized in that, The self-cleaning layer comprises a hydrophobic layer and a conductive heating layer; The forming of the self-cleaning layer comprises: forming the conductive heating layer, the conductive heating layer covering a side surface of the protective layer away from the infrared transparent substrate; forming at least one electrode structure, the electrode structure being located on a side surface of the conductive heating layer away from the protective layer, and being arranged circumferentially around the filter layer; forming the hydrophobic layer, the hydrophobic layer being located on a side surface of the conductive heating layer away from the infrared transparent substrate; the hydrophobic layer is a periodic micro-nano structure or a non-periodic micro-nano structure.

10. The method of claim 8, wherein the self-cleaning long-wave infrared optical filter is prepared by the steps of: The self-cleaning layer comprises the catalytic decomposition layer; The forming of the self-cleaning layer includes: forming the catalytic decomposition layer on a side surface of the protective layer away from the light filtering layer.

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